Resource Accounts

Object Code Deployment is the preferred method for deploying and upgrading smart contracts in Aptos. Resource accounts require developers to generate seeds each time a resource account is created, and upgrading contracts requires specific steps which is prone to error.

A resource account is a developer feature used to manage resources independent of an account managed by a user, specifically publishing modules and providing on-chain-only access control, e.g., signers.

Typically, a resource account is used for two main purposes:

• Store and isolate resources; a module creates a resource account just to host specific resources.
• Publish module as a standalone (resource) account, a building block in a decentralized design where no private keys can control the resource account. The ownership (SignerCap) can be kept in another module, such as governance.

Restrictions

In Aptos, a resource account is created based upon the SHA3-256 hash of the source’s address and additional seed data. A resource account can be created only once; for a given source address and seed, there can be only one resource account. That is because the calculation of the resource account address is fully determined by the former.

An entity may call create_account in an attempt to claim an account ahead of the creation of a resource account. But if a resource account is found, Aptos will transition ownership of the account over to the resource account. This is done by validating that the account has yet to execute any transactions and that the Account::signer_capbility_offer::for is none. The probability of a collision where someone has legitimately produced a private key that maps to a resource account address is improbably low.

Setup

The easiest way to set up a resource account is by:

1. Using Aptos CLI: aptos account create-resource-account creates a resource account, and aptos move create-resource-account-and-publish-package creates a resource account and publishes the specified package under the resource account’s address.
2. Writing custom smart contracts code: in the resource_account.move module, developers can find the resource account creation functions create_resource_account, create_resource_account_and_fund, and create_resource_account_and_publish_package. Developers can then call those functions to create resource accounts in their smart contracts.

Each of those options offers slightly different functionality:

• create_resource_account - merely creates the resource account but doesn’t fund it, retaining access to the resource account’s signer until explicitly calling retrieve_resource_account_cap.
• create_resource_account_and_fund - creates the resource account and funds it, retaining access to the resource account’s signer until explicitly calling retrieve_resource_account_cap.
• create_resource_account_and_publish_package - creates the resource account and results in loss of access to the resource account by design, because resource accounts are used to make contracts autonomous and immutable.

In this example, you will initialize the mint_nft module and retrieve the signer capability from both the resource account and module account. To do so, call create_resource_account_and_publish_package to publish the module under the resource account’s address.

1. Initialize the module as shown in the minting.move example.
2. Call create_resource_account_and_publish_package to publish the module under the resource account’s address, such as in the mint_nft.rs end-to-end example.
3. Retrieve the signer cap from the resource account + module account as shown in the minting.move example.

Note, if the above resource_account signer is not already set up as a resource account, retrieving the signer cap will fail. The source_addr field in the retrieve_resource_account_cap function refers to the address of the source account, or the account that creates the resource account.

For an example, see the SignerCapability employed by the mint_nft function in minting.move.

For more details, see the “resource account” references in resource_account.move and account.move.